Enzymes which are able to degrade cellulose (in the following termed "cellulolytic enzymes" or "cellulases") may be used in paper pulp processing for removing the non-crystalline parts of cellulose, thus increasing the proportion of crystalline cellulose in the pulp, and in animal feed for improving the digestibility of glucans. A further important use of cellulolytic enzymes is for textile treatment, e.g. for reducing the harshness of cotton-containing fabrics (cf., for instance, GB 1 368 599 or U.S. Pat. No. 4,435,307), for soil removal and colour clarification of fabrics (cf., for instance, EP 220 016) or for providing a localized variation in colour to give the fabrics a "stone-washed" appearance (cf., for instance, EP 307 564).
The practical exploitation of cellulolytic enzymes has, to some extent, been set back by the nature of the known cellulase preparations which are often complex mixtures of a variety of single cellulase components, and which may have a rather low specific activity. It is difficult to optimise the production of single components in multiple enzyme systems and thus to implement industrial cost-effective production of cellulolytic enzymes, and their actual use has been hampered by difficulties arising from the need to employ rather larger quantities of the enzymes to achieve the desired effect.
The drawbacks of previously suggested cellulolytic enzymes may be remedied by using single-component enzymes selected for a high specific activity. Single-component cellulases are described in, e.g. WO 91/17243, WO 91/17244 and WO 91/10732.